Menu driven Queue Implementation using Python

# Printing will be handled in the main function so don't use print in the class

class Queue:

# Constructor

def __init__(self, capacity):

self.front = self.size = 0 # Front --> Start

self.rear = capacity - 1 # Rear --> End

self.Q = [None]*capacity

self.capacity = capacity

# if size = capacity then queue is full

def is_full(self):

return self.size == self.capacity

# Check empty

def is_empty(self):

return self.size == 0

# Enque

def enque(self, item):

if self.is_full():

return False

else:

self.rear = (self.rear + 1) % (self.capacity)

self.Q[self.rear] = item

self.size += 1

return True

# Dequeue

def dequeue(self):

if self.is_empty():

return False

else:

item = self.Q[self.front]

self.front = (self.front + 1) % (self.capacity)

self.size -= 1

return item

# Replace any item

def replace(self, item, val):

if item not in self.Q:

return False

else:

pos = self.Q.index(item)

self.Q[pos] = val

return True

# Print the queue

def __str__(self):

return str(self.Q[self.front: self.rear+1])

# Driver program -- Main

def main():

size = input("Enter the queue size : ")

if not size.isdigit():

print("ERROR!! - Wrong Input")

else:

q = Queue(int(size))

ch = int(input("-------[ Select Option ]--------\n1. Enqueue \n2. Dequeue \n3. Replace \n4.Print \n5.Exit\n============\n"))

while ch != 5:

# Switch statements

# Case 1

if ch == 1:

item = input("Enter the value:")

if q.enque(item) == True:

print("EnQueued")

else:

print("Queue is full")

# Case 2

elif ch == 2:

item=q.dequeue()

if item:

print(item," - is Dequeued")

else:

print("Queue is Empty")

# Case 3

elif ch == 3:

item = input("Enter the item to be replaced : ")

val = input("Enter the value to be replaced : ")

if q.replace(item,val):

print("Success")

else:

print("Item not found")

# Case 4

elif ch == 4:

print(q)

# Case 5

elif ch == 5:

print("Logging out...")

return

# Default

else :

print("Wrong Input")

# Next iteration

ch = int(input("-------[ Select Option ]--------\n1. Enqueue \n2. Dequeue \n3. Replace \n4.Print \n5.Exit\n============\n"))

if __name__ == '__main__':

main()

OUTPUT

Enter the queue size : 3 -------[ Select Option ]-------- 1. Enqueue 2. Dequeue 3. Replace 4.Print 5.Exit ============ 1 Enter the value:4 EnQueued -------[ Select Option ]-------- 1. Enqueue 2. Dequeue 3. Replace 4.Print 5.Exit ============ 1 Enter the value:5 EnQueued -------[ Select Option ]-------- 1. Enqueue 2. Dequeue 3. Replace 4.Print 5.Exit ============ 1 Enter the value:6 EnQueued -------[ Select Option ]-------- 1. Enqueue 2. Dequeue 3. Replace 4.Print 5.Exit ============ 4 ['4', '5', '6'] -------[ Select Option ]-------- 1. Enqueue 2. Dequeue 3. Replace 4.Print 5.Exit ============ 2 4 - is Dequeued -------[ Select Option ]-------- 1. Enqueue 2. Dequeue 3. Replace 4.Print 5.Exit ============ 2 5 - is Dequeued -------[ Select Option ]-------- 1. Enqueue 2. Dequeue 3. Replace 4.Print 5.Exit ============ 2 6 - is Dequeued -------[ Select Option ]-------- 1. Enqueue 2. Dequeue 3. Replace 4.Print 5.Exit ============ 2 Queue is Empty -------[ Select Option ]-------- 1. Enqueue 2. Dequeue 3. Replace 4.Print 5.Exit ============ 1 Enter the value:8 EnQueued -------[ Select Option ]-------- 1. Enqueue 2. Dequeue 3. Replace 4.Print 5.Exit ============ 3 Enter the item to be replaced : 8 Enter the value to be replaced : 9 Success -------[ Select Option ]-------- 1. Enqueue 2. Dequeue 3. Replace 4.Print 5.Exit ============ 4 ['9'] -------[ Select Option ]-------- 1. Enqueue 2. Dequeue 3. Replace 4.Print 5.Exit ============ 5